1. Field of the Invention
The invention is related to vehicle sensitive seat belt retractors and in particular to a lock-up mechanism for vehicle sensitive seat belt retractors for locking a child's seat in place.
2. Prior Art
Vehicle sensitive seat belt retractors have gained wide acceptance for automotive use since they provide a greater degree of freedom for the passengers than the conventional types of seat belt retractors which lock up once the seat belt is buckled and the excess webbing retracted by the retractor. In a vehicle sensitive seat belt retractor, the retractor does not lock up, and will allow the seat belt webbing to be extracted with the movement of the buckled passenger. This flexibility allows the passenger a greater degree of freedom to move without being restrained by the seat belt. The vehicle sensitive seat belt retractors normally include an inertia sensor responsive to a sudden change in the vehicle's velocity, such as a crash condition, which automatically locks up the retractor such that the webbing can no longer be extracted, thereby securing the passenger in place.
However, with the recent enactment of laws which require child seats for small children below a predetermined age, the vehicle sensitive retractor systems are inadequate for holding the child's seat in place in the absence of a crash condition. The normal activity of the child is capable of causing the child's seat to be displaced from its desired position resulting in excessive slack in the seat belt. This displacement of the child's seat results in inadequate protection for the child which is contra to the intent of these laws.
The invention is a lock-up mechanism for the vehicle sensitive retractors, which locks the child's seat in place once the seat belt is fastened to the child's seat. This lock-up mechanism is an improvement over the operator actuated lock-up mechanism disclosed by J. W. Frankila and R. L. Stephenson in U.S. Pat. No. 4,327,882.